During drilling operations it is often necessary to drill one or more additional boreholes out from a main wellbore into the surrounding formation in order to stimulate production and increase the ultimate recovery of reserves. A common technique for installing additional boreholes includes cutting, milling or otherwise drilling holes into the main wellbore casing, followed by installing boreholes into the formation surrounding the main wellbore through the casing holes. Various technologies are currently used to install additional boreholes.
For example, one technology for installing boreholes includes deflecting a drill bit to drill a hole in the well casing using a rotary drill device, and subsequently extending the borehole into the surrounding formation using a known fluid jetting technique.
Another technology includes milling a rectangular slot in the well casing using a rotary drill device, and then using a whipstock to deflect a directional drilling string into the surrounding formation.
Another technology includes drilling a hole in the wellbore casing using a mud motor driven drill device, and subsequently jetting an extended borehole into the surrounding formation.
Another technology includes drilling a hole in the wellbore casing using a rotary drill device and subsequently jetting a relatively short hole into the target formation.
Another technology includes jetting extended articulated or horizontal boreholes into the earth using coil tubing as the conveyance means for high pressure fluid from the surface.
Another technology includes utilizing a mud motor connected by a helical spring to a drill bit to cut a hole in the wellbore casing and extending the hole a short distance into the surrounding formation.
Unfortunately, each of these existing technologies require that the string including the drilling means be removed after a single hole is made in the wellbore casing in order to insert a jetting assembly to jet a borehole through the wellbore casing hole into the surrounding formation. Subsequently, the string including the drilling means must be reinserted to make a second hole in the casing. This requires a significant amount of time for installing multiple boreholes.
Other undesirable characteristics associated with these existing technologies include (1) that the installed boreholes cannot be relocated, re-entered and/or re-accessed for stimulation or for the installation of a liner string after the whipstock is re-oriented to a second position for installing a borehole; (2) that the distance to which the boreholes can be installed may be limited to a short distance in the surrounding formation; (3) that holes cannot be made in the casing at different elevations with any certainty of being able to re-enter or re-access those same holes for jetting boreholes into the surrounding formation; (4) that boreholes cannot be installed at different elevations with any certainty of being able to relocate, re-enter and/or re-access those boreholes at a later date; (5) that the boreholes cannot be installed at different vertical elevations in the same direction in a “stacked” fashion; (6) that known downhole orienting tools cannot be removed from the wellbore and then replaced to the same position and orientation to allow both (a) the previously drilled holes in the wellbore casing and (b) subsequently installed boreholes to be relocated, re-entered and/or re-accessed.
A technology is needed that allows for one or more holes to be made in the wellbore casing prior to the installation of boreholes through the holes into the surrounding formation. A technology is also needed that allows for each casing hole and each borehole extending therefrom to be relocated, re-entered, and/or reaccessed.